<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>index</title>
</head>
<body>
	<p>点击按钮,三秒后弹出"hello</p>
	<button onclick="myfunction()">点我</button>
	<script>
		function myfunction () {
			setTimeout(function(){
				alert("hello")
			},3000);
		}
	</script>
</body>
</html>